Add support for custom launch options in the UI

[pinduzera]

I'd like support for being able to use additions run flags within CasaOS custom install/UI.
The main motivator at the moment is that I want to use Jellyfin with gpu encoding, but for that I need support to add one of the additional docker run parameters:

--gpus all (for jellyfin/jellyfin, official image)
--runtime=nvidia (for linuxserver/jellyfin, supported by casaOS)

Of course I can always run the container directly within the terminal, but that would defeat the purpose of casaOS.